The overall goal of this project is to characterize the rat dopamine D2 receptor gene system and utilize it in a model to study the effect of neuroleptics on the dopamine D2 receptor system as it may relate to schizophrenia. This will be accomplished through a series of specific aims. We will first characterize and develop specific probes to each of the different rat dopamine D2 receptor mRNAs expressed in the brain. This will be done using the polymerase chain reaction technique with synthetic DNA oligomers. Attempts will be made to correlate the different forms seen in the rat brain with those seen in the human brain. A second set of studies will be done to identify the specific anatomical sites of expression, both at low resolution using RNA isolated from dissected tissue sections in a nuclease hybridization assay, as well as in situ hybridization for high resolution semi-quantitative studies. These studies will serve as the base for the subsequent acute and chronic regulatory studies. A third specific aim will be to utilize specific lesions of the substantia nigra/ventral tegmental area to study the relationship between dopamine D2 receptor and receptor mRNA changes using receptor binding assays, solution hybridization/nuclease protection assays, and in situ hybridization histochemistry. A fourth specific aim will be to use the rat as a model system to study alterations in dopamine receptor subtype gene expression associated with chronic neuroleptic will allow us to identify specific receptor subtypes that are more affected by neuroleptics that have greater efficacy in the treatment of schizophrenia in order to better direct drug studies in humans. Finally, in order to begin to elucidate mechanisms associated with any changes in dopamine D2 receptor mRNA expression, we will perform acute studies with haloperidol and/or other neuroleptics to analyze changes in nuclear cytoplasmic D2 receptor mRNAs. Such studies should show us at which level the neuroleptics are affecting the pathway of gene expression for the dopamine D2 receptor subtypes. It is anticipated that together these studies will provide us with a better understanding of he dopamine D2 receptor system in a model where we can more accurately manipulate the environment and hopefully see how changes in the system may be involved in the efficacy of the disease.